Abstract: Aiming at fluid-structure interaction problems between a submerged structure subjected to shock waves and infinite acoustic fluid, a transient analysis method is proposed based on the scaled boundary finite element method (SBFEM) and finite element method (FEM). The infinite fluid is discretized by the SBFEM and the bounded domain such as the submerged structure is modeled by the FEM. Using the acoustic approximation method, the proposed method decomposes the loadings on the submerged structure applied by infinite fluid into shock wave loadings and scattered wave loadings. Shock wave loadings is determined by the underwater shock wave theory, while scattered wave loadings is evaluated by the SBFEM. A time-domain recursive formulation is proposed to improve the SBFEM dynamic mass matrix calculation efficency. Numerical examples results show the accuracy of the proposed analysis method and the time-domain recursive formulation.